Our work for the coming year will be mainly directed toward (1) determining the cell-type-specificity of inhibition of cell aggregation by non-agglutinating, modified D. biflorus lectin and by anti-retina Fab antibody fragments; (2) beginning the isolation and characterization of the cell surface sites recognized by the aggregation-blocking D. biflorus lectin; and (3) continuing the development of a new method suitable for the routine measurement of tissue sigma 's (intercellular adhesive energies). Sigma 's are the physical parameters of intercellular adhesiveness which evidently act to guide cells into specific configurations relative to one another and to extracellular contact surfaces. A "proper" set of sigma 's can govern proper organogenesis, while a disturbed set of sigma 's could cause malformations or invasiveness.